[PATCH 2/4] mtd: spi-nor: Allow flashes to specify MTD writesize

[tkuw584924 at gmail.com]

From: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>

Some flashes like the Infineon SEMPER NOR flash family use ECC. Under
this ECC scheme, multi-pass writes to an ECC block is not allowed.
In other words, once data is programmed to an ECC block, it can't be
programmed again without erasing it first.

Upper layers like file systems need to be given this information so they
do not cause error conditions on the flash by attempting multi-pass
programming. This can be done by setting 'writesize' in 'struct
mtd_info'.

Set the default to 1 but allow flashes to modify it in fixup hooks. If
more flashes show up with this constraint in the future it might be
worth it to add it to 'struct flash_info', but for now increasing its
size is not worth it.

Signed-off-by: Takahiro Kuwano <Takahiro.Kuwano at infineon.com>
---
 drivers/mtd/spi/spi-nor-core.c | 3 ++-
 include/linux/mtd/spi-nor.h    | 1 +
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/spi/spi-nor-core.c b/drivers/mtd/spi/spi-nor-core.c
index f86003ca8c..1bfef6797f 100644
--- a/drivers/mtd/spi/spi-nor-core.c
+++ b/drivers/mtd/spi/spi-nor-core.c
@@ -2789,6 +2789,7 @@ static int spi_nor_init_params(struct spi_nor *nor,
 	memset(params, 0, sizeof(*params));
 
 	/* Set SPI NOR sizes. */
+	params->writesize = 1;
 	params->size = info->sector_size * info->n_sectors;
 	params->page_size = info->page_size;
 
@@ -4078,7 +4079,7 @@ int spi_nor_scan(struct spi_nor *nor)
 	mtd->dev = nor->dev;
 	mtd->priv = nor;
 	mtd->type = MTD_NORFLASH;
-	mtd->writesize = 1;
+	mtd->writesize = params.writesize;
 	mtd->flags = MTD_CAP_NORFLASH;
 	mtd->size = params.size;
 	mtd->_erase = spi_nor_erase;
diff --git a/include/linux/mtd/spi-nor.h b/include/linux/mtd/spi-nor.h
index d1dbf3eadb..0d37a806c4 100644
--- a/include/linux/mtd/spi-nor.h
+++ b/include/linux/mtd/spi-nor.h
@@ -436,6 +436,7 @@ enum spi_nor_pp_command_index {
 
 struct spi_nor_flash_parameter {
 	u64				size;
+	u32				writesize;
 	u32				page_size;
 	u8				rdsr_dummy;
 	u8				rdsr_addr_nbytes;
-- 
2.34.1